This invention relates to needle devices for medical use. It was developed primarily for skin prickers and will be described mainly in those terms. However, it could be applicable to injection devices.
Skin prickers are used for various medical purposes, one being to draw a drop of blood for analysis. Usually, that just requires a lancet with a single needle. But there is a tuberculin test, known as the Heaf Test, where a number of needles are driven into the skin, which is previously smeared with a substance that is carried by the needles into the blood vessels below the skin. The subsequent reaction is an indication of whether the test is positive or negative.
For this test it is necessary to ensure that the force of application of the needle lies within an upper and lower limit to maintain the reliability of the test.